Most positioning devices (or navigation devices) utilizes technologies of Global Position System (GPS). GPS is a combination of wireless communication technology and satellite technology for providing accurate positioning, velocity and time information to users. With advances in satellite-related technologies, applications of GPS have been gradually spreads from military usage to our daily life. The most common application of GPS includes positioning a target item and navigation.
Positioning and navigation functions of the GPS rely on mutual cooperation between satellites, positioning devices and navigation software. However, the positioning device occasionally fails to receive any positioning signal sent from the satellites because the positioning signals might be obscured by buildings in some cases. For example, when user is located inside a building (e.g., airport terminal, skyscraper, underpass or tunnel) or surrounded by tall buildings in a metropolitan area, the positioning device carried by the user fails to receive any satellite signal, such that the positioning function of the positioning device will be failed. In this case, if the positioning function is needed, users must move the positioning device to outdoor area or open space in order to receive the satellite signals, and it is inconvenient to users.
In addition, the positioning device located in the metropolitan area usually encounters an issue of multi-path effect, which means the satellite signals are reflected by buildings, mirrors, water surfaces or other reflective surfaces to antenna of the positioning device. The satellite signals reflected through different paths will disrupt judgments of the positioning device and cause positioning errors.